THE NUCLEO-PROTEIDS. 67 



researches of Kossel, who obtained a carbohydrate from the nucleic acid of 

 yeast. 1 



Kossel and Neumann 2 have further shown that adenylic acid yields also 

 a new acid called thymic acid, precipitable as a barium salt (C 16 H^N 3 P 2 12 Ba). 

 The acid is readily soluble in cold water, and differs from nucleic acid in not 

 being precipitated by mineral acids. 3 



Kesearches such as these show how complicated the subject is, and 

 how much yet remains to be discovered, especially regarding the nuclein 

 acids. The nuclein bases are comparatively simple, and the principal 

 ones may be arranged in two groups : 



Adenine has the formula C 5 H 5 N 5 ; on heating it with sulphuric acid, 

 Nil is replaced by 0, and hypoxanthine is formed : 



C 5 H 4 N 4 .NH + H 2 = C H 4 N 4 + NH 3 



(adenine) (water) (hypoxanthine) (ammonia) 



Both substances contain a radicle, C 5 H 4 N 4 , which Kossel terms adenyl ; 

 adenine is its imide, hypoxanthine its oxide. The following equation 

 shows a similar relationship between guanine and .xanthine : 



C 5 H 4 N 4 O.NH + H 2 = C 5 H 4 N 4 2 + NH 3 



(guanine) (water) (xanthine) (ammonia) 



On comparing the formulae of hypoxanthine and xanthine with uric 

 acid (C 5 H 4 N 4 3 ), we see their close relationship. Leaving aside other 

 possible ways in which uric acid is undoubtedly formed in the organism, 

 we have here a way in which uric acid may arise by oxidation 

 from the nuclein bases, and thus ultimately from the nuclei of cells. 4 

 The name " alloxuric bases " for these substances was suggested by 

 Kriiger and Wulff. 5 They are often spoken of as the " xanthine bases." 



The nucleo-proteids. These are compounds of nuclein with pro- 

 teids. The amount of proteid matter is large, and the substances in 

 question give the reactions of proteids, and in their solubilities approach 

 very nearly to the globulins. On gastric digestion the nuclein they con- 

 tain is left as an insoluble residue, but on pancreatic digestion a good 

 deal of the nuclein is dissolved, and presumably, when this occurs in the 

 body, is absorbed. 6 



Hammarsten divides the nucleo-proteids into two classes ; the first, to 

 which he restricts that name, yields true nuclein on gastric digestion ; 

 the other class he calls nucleo-albumins ; these yield pseudo-nuclein on 

 gastric digestion, and include caseinogen and vitellin. In addition to 

 these, there are the phospho-gluco-proteids, which have already been 

 described (p. 64). 



Nucleo-proteids, using the term in the widest sense, are obtain- 



1 Kossel and Neumann, JBer. d. deutscli. chem. Gesellsch., Berlin, Bd. xxvii. S. 2215. 



2 Ztschr. f. pliysiol. Chem., Strassburg, Bd. xxii. S. 74. 



a It was later obtained from spermatozoa nuclein (Kossel, ibid., p. 188). Milroy (ibid., 

 1896, Bd. xxii. S. 307) states that the precipitate formed on adding nucleic acid to a solu- 

 tion of albumin resembles true nuclein in its characters ; whereas the precipitate produced 

 by thymic acid is somewhat similar to para-nuclein or pseudo-nuclein. 



4 This subject has been specially taken up by Horbaczewski (Sitzungsb. d. k. Akad. d. 

 Wissensch,, Wien, Bd. c.), who has pointed out the close relationship between uric acid 

 formation and leucocytosis. Diet increases uric acid formation by leading to an increase 

 of leucocytes, or possibly, as some recent investigators think, the increase is chiefly due 

 to the nuclein in the food (Weintrand, Chem. Centr.-BL, Leipzig, 1895, Bd. ii. S. 54, 

 234, 310). See also Umber, Ztschr. f. klin. Med., Berlin, 1896, Bd. xxix. S. 174 ; Camerer, 

 Ztschr. f. BioL, Miinchen, 1896, Bd. xxxiii. S. 139. 



5 Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xx. S. 176. . 



6 Popoff, Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 533 ; Gumlich, ibid., S. 508. 



